"What the application does and how it behaves is all that matters."
I'm hard pressed to find a rebuttal to this, if only for the reason that implementation is the goal. No one will ask you to write an application in Python, "and who cares what it does". The very opposite is true - no one cares what it's written in as long as it's the necessary implementation.
From here I would like to address my "point" that tech stack and framework don't matter. I think that we're actually on the same page here save for some sloppy wording on my part. I concede that on a per-project basis framework and stack matter. They quite clearly do, and I agree with you.
I would still like to argue that they don't matter as much as we like to think. To use the example you gave - PHP - depending on your purpose, your required implementation, PHP is still a powerful and useful tool. It's easier to work with than many other technologies for certain kinds of solutions. At the same time, it might be a better idea to write a solution on Rails for any number of reasons. These are specific to each project. At the end of the day though, you can successfully implement any number of solutions on a great many different stacks with no great change to implementation. I can write an application and use either PHP or Rails for the backend, Angular or Backbone for the frontend framework if I have one, and for the end user there will be ultimately no difference. I can run a PostgreSQL or a MongoDB database and they won't be able to tell the difference. If this is the case then, what makes a good application? It is the people writing the code, architecting, and meeting the challenges in ways that work with the chosen frameworks and technology stacks. It seems to me that the end result, then, is reached by people and not by stacks or frameworks.
Sorry for the long reply. No harm if you don't reply to it.